Certain Genus 3 Siegel Cusp Forms with Level are Determined by their Fundamental Fourier Coefficients (2507.17002v1)

Abstract: We prove that vector-valued genus 3 Siegel cusp forms for $\Gamma_0^3(N)$ with certain nebentypus are determined by their fundamental Fourier coefficients, assuming $N$ is odd and square-free. A key step in our proof involves strengthening the known corresponding genus 2 result. More precisely, we show that genus 2 Siegel cusp forms for $\Gamma_0^2(N)$ with certain nebentypus are determined by their fundamental Fourier coefficients whose discriminants are coprime to $N$. We also prove that Jacobi forms of fundamental index with discriminant coprime to the odd level $N$ are determined by their primitive theta components.